Sjouwerman, R. | Search bioRxiv

bioRxiv2019

The neurofunctional basis of affective startle modulation in humans - evidence from combined facial EMG-fMRI

The startle reflex, a protective response elicited by an immediate, unexpected sensory event, is potentiated when evoked during threat and inhibited during safety. In contrast to skin conductance responses or pupil dilation, modulation of the startle reflex is valence-specific and considered the cross-species translational tool for defensive responding.\n\nRodent models implicate a modulatory pathway centering on the brainstem (i.e., nucleus reticularis pontis caudalis, PnC) and the centromedial amygdala (CeM) as key hubs for flexibly integrating valence information into differential startle magnitude.\n\nWe employed innovative combined EMG-fMRI measurements in two independent experiments and samples and provide converging evidence for the involvement of these key regions in the modulatory acoustic startle reflex pathway in humans. Furthermore, we provide the crucial direct link between EMG startle eye-blink magnitude and neural response strength.\n\nWe argue that startle-evoked amygdala responding and its affective modulation may hold promise as an important novel tool for affective neuroscience.

neuroscience↗

bioRxiv2017

Individual differences in fear learning: Specificity to trait-anxiety beyond other measures of negative affect, and mediation via amygdala activation

Negative emotionality is a well-established and stable risk factor for affective disorders. Individual differences in negative emotionality have been linked to associative learning processes which can be captured experimentally in fear conditioning paradigms. Literature suffers from underpowered samples, suboptimal methods, and an isolated focus on single questionnaires and single outcome measures. Here, we apply multivariate and dimensional approaches for three commonly investigated questionnaires in the field (STAI-T, NEO-FFI Neuroticism, Intolerance of Uncertainty Scale) across multiple analysis units (ratings, skin conductance, startle, BOLD-fMRI) during fear acquisition-training in two large samples (NStudy1=356; NStudy2=113). We investigate whether the specific or shared variance of these questionnaires is linked with CS-discrimination in specific outcome measures (Study 1). We identify a significant negative association between STAI-T and CS-discrimination in SCRs and between Intolerance of Uncertainty and CS-discrimination in startle responding. Yet, correlation coefficients for all questionnaire-outcome measure combinations did not differ significantly from each other. In Study 2 the STAI-T score was positively associated with CS-discrimination in a number of brain areas linked to conditioned fear (amygdala, putamen, thalamus), but not to SCRs or ratings. Importantly, we replicate potential sampling biases between fMRI and behavioral studies regarding anxiety levels. We discuss the implications of these results.

neuroscience↗